From e1d86973312075ae3a5d79a70759908f36dfd350 Mon Sep 17 00:00:00 2001
From: Christian <christian.kratky@googlemail.com>
Date: Tue, 13 Mar 2018 20:22:48 +0100
Subject: [PATCH] Fix wrong parsing and generating of MqttConnAck for version
 3.1.0

---
 .../Serializer/MqttPacketSerializer.cs        | 35 ++++++++++++-------
 .../MqttPacketSerializerTests.cs              | 19 +++++++---
 2 files changed, 37 insertions(+), 17 deletions(-)

diff --git a/Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketSerializer.cs b/Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketSerializer.cs
index 6491e281..63a3c646 100644
--- a/Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketSerializer.cs
+++ b/Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketSerializer.cs
@@ -75,7 +75,7 @@ namespace MQTTnet.Serializer
             }
         }
 
-        private static MqttBasePacket Deserialize(MqttPacketHeader header, MqttPacketReader reader)
+        private MqttBasePacket Deserialize(MqttPacketHeader header, MqttPacketReader reader)
         {
             switch (header.ControlPacketType)
             {
@@ -278,20 +278,22 @@ namespace MQTTnet.Serializer
             return packet;
         }
 
-        private static MqttBasePacket DeserializeConnAck(MqttPacketReader reader)
+        private MqttBasePacket DeserializeConnAck(MqttPacketReader reader)
         {
-            var variableHeader1 = reader.ReadByte();
-            var variableHeader2 = reader.ReadByte();
+            var packet = new MqttConnAckPacket();
 
-            var packet = new MqttConnAckPacket
+            var firstByteReader = new ByteReader(reader.ReadByte());
+
+            if (ProtocolVersion == MqttProtocolVersion.V311)
             {
-                IsSessionPresent = new ByteReader(variableHeader1).Read(),
-                ConnectReturnCode = (MqttConnectReturnCode)variableHeader2
-            };
+                packet.IsSessionPresent = firstByteReader.Read();
+            }
+
+            packet.ConnectReturnCode = (MqttConnectReturnCode)reader.ReadByte();
 
             return packet;
         }
-
+        
         private static void ValidateConnectPacket(MqttConnectPacket packet)
         {
             if (packet == null) throw new ArgumentNullException(nameof(packet));
@@ -373,14 +375,21 @@ namespace MQTTnet.Serializer
 
         private byte Serialize(MqttConnAckPacket packet, MqttPacketWriter writer)
         {
-            var connectAcknowledgeFlags = new ByteWriter();
-
-            if (ProtocolVersion == MqttProtocolVersion.V311)
+            if (ProtocolVersion == MqttProtocolVersion.V310)
             {
+                writer.Write(0);
+            }
+            else if (ProtocolVersion == MqttProtocolVersion.V311)
+            {
+                var connectAcknowledgeFlags = new ByteWriter();
                 connectAcknowledgeFlags.Write(packet.IsSessionPresent);
+                writer.Write(connectAcknowledgeFlags);
+            }
+            else
+            {
+                throw new MqttProtocolViolationException("Protocol version not supported.");
             }
 
-            writer.Write(connectAcknowledgeFlags);
             writer.Write((byte)packet.ConnectReturnCode);
 
             return MqttPacketWriter.BuildFixedHeader(MqttControlPacketType.ConnAck);
diff --git a/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs b/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
index 072e1a93..1111d907 100644
--- a/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
+++ b/Tests/MQTTnet.Core.Tests/MqttPacketSerializerTests.cs
@@ -119,10 +119,10 @@ namespace MQTTnet.Core.Tests
         {
             var p = new MqttConnAckPacket
             {
-                ConnectReturnCode = MqttConnectReturnCode.ConnectionAccepted
+                ConnectReturnCode = MqttConnectReturnCode.ConnectionRefusedNotAuthorized
             };
 
-            SerializeAndCompare(p, "IAIAAA==", MqttProtocolVersion.V310);
+            SerializeAndCompare(p, "IAIABQ==", MqttProtocolVersion.V310);
         }
 
         [TestMethod]
@@ -137,6 +137,17 @@ namespace MQTTnet.Core.Tests
             DeserializeAndCompare(p, "IAIBBQ==");
         }
 
+        [TestMethod]
+        public void DeserializeV310_MqttConnAckPacket()
+        {
+            var p = new MqttConnAckPacket
+            {
+                ConnectReturnCode = MqttConnectReturnCode.ConnectionRefusedNotAuthorized
+            };
+
+            DeserializeAndCompare(p, "IAIABQ==", MqttProtocolVersion.V310);
+        }
+
         [TestMethod]
         public void SerializeV311_MqttDisconnectPacket()
         {
@@ -397,9 +408,9 @@ namespace MQTTnet.Core.Tests
             Assert.AreEqual(expectedBase64Value, Convert.ToBase64String(Join(chunks)));
         }
 
-        private static void DeserializeAndCompare(MqttBasePacket packet, string expectedBase64Value)
+        private static void DeserializeAndCompare(MqttBasePacket packet, string expectedBase64Value, MqttProtocolVersion protocolVersion = MqttProtocolVersion.V311)
         {
-            var serializer = new MqttPacketSerializer();
+            var serializer = new MqttPacketSerializer { ProtocolVersion = protocolVersion };
 
             var buffer1 = serializer.Serialize(packet);